Detection of residual bacitracin A, colistin A, and colistin B in milk and animal tissues by liquid chromatography tandem mass spectrometry

Analysing polypeptide antibiotics residues in animal muscle tissues: The crucial role of HRMS

A confirmatory method for the determination of polypeptide antibiotics (bacitracin, colistin, and polymyxin B) in muscle samples has been developed. Extraction is performed with acidified methanol, and a clean-up step by solid-phase extraction with polymeric cartridges is applied. Separation by ultra-high performance liquid chromatography (UHPLC) is carried out using a solid core C18 column and gradient elution with water/acetonitrile containing 0.2% formic acid. High-resolution mass spectrometry (HRMS) (Q-Orbitrap) detection using different working modes has proved to be highly advantageous in eliminating interfering signals from endogenous matrix components. The analytical method has been successfully validated according to Commission Regulation 2021/808/EU and is currently used in a public health laboratory involved in veterinary medicines residue surveillance activities.

Electrochemical immunosensor for the detection of colistin in chicken liver

An innovative amperometric immunosensor has been developed to detect antibiotic colistin from the chicken liver. Colistin is a antibacterial peptide that has been barred for human consumption, but it is being commonly used as a veterinary drug, and as a feed additive for livestock. In the present work, an immunosensor was developed by immobilizing an anti-colistin Ab onto the CNF/AuNPs surface of the screen-printed electrode. The sensor records electrochemical response in the chicken liver spiked with colistin with CV. Additionally, the characterization of electrode surface was done with FE-SEM, FTIR, and EIS at each step of fabrication. The lower LOD was 0.89 μgKg-1, with a R 2 of 0.901 using CV. Further validation of the immunosensor was conducted using commercial chicken liver samples, by comparing the results to those obtained using traditional methods. The fabricated immunosensor showed high specificity towards colistin, which remained stable for 6 months but with a 13% loss in the initial CV current.

Quantum dot-based fluorescence immunosorbent assay for the rapid detection of bacitracin zinc in feed samples

Bacitracin zinc (BAC), a polypeptide antibiotic, is utilized as a feed additive due to its ability to promote growth in animals. However, the abuse of BAC can lead to a great threat to food safety. Therefore, there is an urgent need to develop a rapid and sensitive detection method. In this study, a monoclonal antibody (mAb) against BAC with excellent sensitivity and specificity was obtained. For the first time, quantum dots (QDs) were conjugated with the prepared mAb against BAC and rabbit anti-mouse antibody to fabricate a direct and an indirect competitive fluorescence-linked immunosorbent assay (dc-FLISA and ic-FLISA) to detect BAC. The IC₅₀ of dc-FLISA and ic-FLISA were 0.28 ng/ml and 0.17 ng/ml, respectively. The limits of detection were 0.0016 ng/ml and 0.001 ng/ml, respectively, and the detection ranges were 0.0016-46.50 ng/ml and 0.001-35.65 ng/ml, respectively. In addition, the recovery rate of the two methods ranged from 93.5% to 112.0%, and the coefficient of variation (CV) was less than 10%. Therefore, the methods developed in this work have the merits of low cost, simple operation, and high sensitivity, which provide an effective analytical tool for BAC residue detection in feed samples.

Development of a liquid chromatography-tandem mass spectrometry method to determine colistin, bacitracin and virginiamycin M1 at cross-contamination levels in animal feed

Cross-contamination of animal feed with antibiotics may occur during manufacturing in feed mills, because shared production lines can be used for medicated and non-medicated feed, but may also occur during transport, storage and at the farm level. This is a major issue in the current context where antimicrobial usage must be controlled in order to maintain their effectiveness. A LC-MS/MS method was developed for the determination of colistin, bacitracin A and virginiamycin M1 in feed for pigs, poultry and rabbits at concentrations similar to those encountered in cross-contamination. After investigating various issues related to colistin behaviour and matrix effects, we successfully validated this method according to the requirements of European regulations in terms of linearity, trueness, precision, limit of quantification and limit of decision. Trueness ranged 88.6-107.8% and precision ranged 12.6-21.2%. We then applied this method to the analysis of medicated pig feed to check the performance of the method on "real" samples of medicated feed. We subsequently analysed non-medicated pig, and rabbit feed samples, collected directly on farms, to check the rate of cross-contamination. No samples were contaminated by colistin, bacitracin, or virginiamycin.

Simultaneous determination of multiple polypeptide antibiotics residues in lake water by lyophilization combined with liquid chromatography-tandem mass spectrometry

It is significant to develop a method for the simultaneous determination of multiple polypeptide antibiotics residues in lake water because of the emergence of multidrug-resistant microorganisms in water. A sensitive, eco-friendly and simple method was developed for the determination of multiple polypeptide antibiotics, including vancomycin, teicoplanin, polymyxin B, colistin and bacitracin A in lake water using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Water samples were lyophilized to enrich them after adjusting the pH to 3. Then, 80% methanol in water containing 0.1% formic acid was used to reconstitute the residues for LC-MS/MS analysis. The results showed that target compounds were well separated and detected under the optimum instrumental conditions. The limits of detection and the limits of quantification of polypeptide antibiotics were in the range of 0.01 - 0.1 and 0.02 - 0.2 ng mL-1, respectively. The matrix-matched calibration curves of all compounds were linear in the calibration range of 1 - 200 ng mL-1. At three spiked levels of 0.2 (0.04), 0.4 (0.1) and 1.0 (0.2) ng mL-1 in lake water, the average recoveries of analytes were higher than 70%, except for teicoplanin, with relative standard deviations of less than 20%. Compared with other common sample pretreatment methods, the lyophilization process is simpler and more eco-friendly, achieving the simultaneous detection of multiple polypeptide antibiotics in lake water. The developed method is successfully applied to the routine monitoring of polypeptide antibiotics residues in lake water.

Determination of Colistin B in Chicken Muscle and Egg Using Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

Colistin, an imperative member of the polymyxin group, is a cationic peptide antibiotic. Itis also known as polymyxin E, but this peptide antibiotic has been forbidden for human consumption due to its high toxicity. Regrettably, this antibiotic is utilized as a feed additive and veterinary drug for animals. Due to the toxicity of colistin, the presence of its residue in the animal system represents a threat to human health regarding the consumption of meat, especially chicken. A novel method was proposed for quantifying colistin B in chicken muscles and eggs using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). In this method, extraction of colistin B from samples was achieved by mixing the sample with acidified methanol:water (1/1, v/v), followed by centrifugation and filtration by a membrane filter excluding solid-phase extraction (SPE) clean up, as well as evaporation steps. The analysis was conducted by optimized liquid chromatography-tandem mass spectrometry (LC-MS/MS), and method performance was assessed in terms of the limit of quantitation, specificity, selectivity, precision, linearity and recovery in coherence with the guidelines of SANTE and the Commission Decision 2002/657/EC. The result obtained from the study showed the limit of quantitation (LOQ) as 10 µg Kg^-1 for muscles and 5 µg Kg^-1 for eggs, with acceptable recoveries along with precision. The linearity was plotted in the range of 5-25 µg L^-1 (solvent) for egg and 10-50 µg Kg^-1 (matrix-matched) for muscles. The result of average recoveries showed the value of 70-94% (3.3-12% relative standard deviation (RSD)) for chicken muscles and 88-107% (2.5-18.6% RSD) for egg samples, which meets the criteria for acceptability of method according to both SANTE and 2002/657/EC guidelines. This proposed protocol provides a cost-effective solution for food testing labs by reducing the cost of the sample preparation by 60% along with the time required for SPE cleanup. Further, the optimized method was also tested on real samples collected from nearby provinces in Solan city, Himachal Pradesh, India, and three out of 20 muscles were found to have colistin B in the range of 50-560 µg Kg^-1.

Understanding of Colistin Usage in Food Animals and Available Detection Techniques: A Review

Progress in the medical profession is determined by the achievements and effectiveness of new antibiotics in the treatment of microbial infections. However, the development of multiple-drug resistance in numerous bacteria, especially Gram-negative bacteria, has limited the treatment options. Due to this resistance, the resurgence of cyclic polypeptide drugs like colistin remains the only option. The drug, colistin, is a well-known growth inhibitor of Gram-negative bacteria like Acinetobacter baumanni, Enterobacter cloacae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Technological advancements have uncovered the role of the mcr-1(mobilized colistin resistance) gene, which is responsible for the development of resistance in Gram-negative bacteria, which make them distinct from other bacteria without this gene. Additionally, food animals have been determined to be the reservoir for colistin resistance microbes, from which they spread to other hosts. Due to the adverse effects of colistin, many developed countries have prohibited its usage in animal foods, but developing countries are still using colistin in animal food production, thereby imposing a major risk to the public health. Therefore, there is a need for implementation of sustainable measures in livestock farms to prevent microbial infection. This review highlights the negative effects (increased resistance) of colistin consumption and emphasizes the different approaches used for detecting colistin in animal-based foods as well as the challenges associated with its detection.

Analysis of peptide antibiotic residues in milk using liquid chromatography-high resolution mass spectrometry (LC-HRMS)

A liquid chromatography-high resolution mass spectrometry (LC-HRMS) method was developed and validated for the determination of residual peptide antibiotics (bacitracin A, colistin A and B, enramycin A and B, virginiamycin M1 and S1) in bovine milk. LC-HRMS accurate mass data provided the necessary selectivity and sensitivity to quantitate and identify these important antibiotics in milk at residue levels without extensive sample preparation. Milk samples were extracted using 0.3% formic acid in acetonitrile with 0.06% trifluoroacetic acid added to improve peptide recoveries. Sample clean-up was minimal with an aliquot of the extract evaporated and reconstituted in a formic acid/water-acetonitrile mixture and then filtered. LC separation was performed with 0.3% formic acid in the gradient to improve the peak shape and reproducibility of the peptide analytes. A Quadruple-Orbitrap HRMS instrument with full-scan MS1 data collection followed by all-ion-fragmentation was used to obtain the exact mass of the precursor and confirmatory product ions. One advantage of LC-HRMS is that a combination of multiple precursor ions, including different charge states or adducts, can be used for quantification. The method was validated at four concentration levels ranging from 12.5 to 200 ng/g in three types of bovine milk. For bacitracin A, colistins and enramycins, the average recoveries compared to solvent standards ranged between 70% and 120%. Average recoveries for virginiamycin residues in milk extracts were unacceptably high (up to 138%) using solvent standards, but recoveries using matrix-matched calibration were determined to be 90-115%. Matrix effects were found to be less than 25% for the other analytes when internal standard correction was used for the colistins. Intra-day relative standard deviations were generally below 15%. The method detection limits for the peptide antibiotic residues in milk (0.5 to 5.5 ng/g) were well below regulatory levels of concern.

Determination of Polypeptide Antibiotic Residues in Food of Animal Origin by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

A novel UHPLC-MS/MS method for the determination of polypeptide antibiotic residues in animal muscle, milk, and eggs was developed and validated. Bacitracin A, colistin A, colistin B, polymyxin B1, and polymyxin B2 were extracted from the samples with a mixture of acetonitrile/water/ammonia solution 25%, 80/10/10 (v/v/v), and put through further evaporation, reconstitution, and filtration steps. The chromatographic separation was performed on a C18 column in gradient elution mode. Mass spectral acquisitions were performed in selective multiple reaction monitoring mode by a triple quadrupole mass spectrometer. The method was validated according to the criteria of Commission Decision 2002/657/EC. The method quantifies polypeptides in a linear range from 10 to 1000 μg kg⁻¹, where the lowest concentration on the calibration curve refers to the limit of quantification (LOQ). The recoveries ranged from 70 to 99%, the repeatability was below 13%, and within-laboratory reproducibility was lower than 15%. The decision limit (CCα) and detection capability (CCβ) values were calculated, and ruggedness and stability studies were performed, to fulfill the criteria for confirmatory methods. Moreover, the developed method may also be used for screening purposes by its labor efficiency.

Colloidal gold-based immunochromatographic strip assay for the rapid detection of bacitracin zinc in milk

In this study, a murine monoclonal antibody (mAb) of 6D2-G10 against bacitracin zinc (BAC) was produced and applied to an immunochromatographic strip (ICS) for the initial detection of BAC in milk. The ICS with a cut-off value of 25 ng/mL could be perceived by the naked eye within 10 min. With the assist of the strip reader, the limit of detection (LOD) was measured as 0.82 ng/mL, the half-maximal inhibitory concentration (IC₅₀) was recorded as 3.16 ng/mL, and the linear detection range was from 0.97 to 10.30 ng/mL. The recoveries ranged from 87.7% to 96.0% with the highest coefficient of variation (CV) of 9.1% in the intra-assay and from 84.3% to 90.2% with the highest CV of 10.7% in the inter-assay. In short, the established ICS provided a serviceable analytical tool for qualitatively and quantitatively monitoring BAC in milk.

Evaluation of co-delivery of colistin and ciprofloxacin in liposomes using an in vitro human lung epithelial cell model

Respiratory tract infections caused by multidrug-resistant Gram-negative bacteria are serious burdens to the public. Our previous findings indicated that co-loading of colistin and ciprofloxacin via liposomes improved in vitro antimicrobial activities against multidrug resistant Pseudomonas aeruginosa as compared to the monotherapies. The current study aims to investigate the transport behavior of colistin and ciprofloxacin in liposomes using the in vitro Calu-3 cell monolayer, which is a lung epithelial model cultured under the air-interfaced condition. The cell viability results demonstrated that there was no obvious toxicity of cells exposed to single or co-administered drugs at the concentration ≤500 μg/mL. Transport of ciprofloxacin into the cells was easier than that of colistin, which reached a plateau rapidly. Colistin was less trapped in the mucus or adhered to the apical cell membrane, and less transported across the cell monolayer than ciprofloxacin. The deposition of ciprofloxacin on the apical side increased over time (from 1 to 4 h). There was no drug-drug interaction observed during the transport of ciprofloxacin and colistin across the cell monolayer, when they were dosed together in the solution form. The amount of drug transported across the cell monolayer was decreased in both agents when loaded in liposomes. Both drugs were more trapped in the mucus or more adhered to the apical side cell membrane of the cell monolayer when they were in liposomes. This study demonstrated that co-delivery of colistin and ciprofloxacin in a single liposome can reduce transport capacity of both drugs across the lung epithelial cell monolayer and enhance drug retention on the lung epithelial surfaces; therefore, it is a promising approach to treat the respiratory infections caused by multidrug resistant Pseudomonas aeruginosa.

Antibiotic residues in milk: Past, present, and future

Now-a-days, various types of antibiotics are being used worldwide in veterinary sector indiscriminately for promotion of growth and treatment of the livestock. Significant portions of antibiotics are released through milk of dairy animals unaltered and exert serious harmful effects on human health. This review evaluates and compare researches on antibiotic residues in milk in published literatures from Pubmed, CrossRef, CAB direct, DOAJ, JournalTOCs, AGRICOLA, ScientificGate, Electronic Journals Library, CAB abstracts, Global Health Databases, Global Impact Factor, Google Scholar, Park Directory of Open Access Journals, BanglaJOL and ISC E-Journals. Antibiotics residue in milk was first detected in 60s and then with an increasing trend with highest after 2,000 (188). The highest no. of works, 49 (21.87%) were accomplished in China, followed by Spain, 30 (13.39%); Germany, 11 (4.91%); and USA, 10 (4.46%). Continent-wise highest researches are published from Europe, 105 (46.88%), followed by Asia, 77 (34.38%); South America, 18 (8.04%); North America, 16 (7.14%); and Africa, 8 (3.57%). For detection, Bovine milk sample is mostly used, 193 (86.16%), followed by ovine, 19 (8.48%); and caprine, 14 (6.25%). Acetonitrile was used in maximum cases (77) for processing the samples. Chromatographic technique was the highest, 115 (51.34%) for detection. Residue of β-lactam group have been detected mostly 133 (36.54%), followed by tetracyclines, 51 (14.01%); fluoroquinolones, 49 (13.46%); sulfonamides, 46 (12.64%); and aminoglycosides, 38 (10.44%). This review observe that antibiotics residues are more common in milk samples that are being manifested in increasing researches on antibiotic detection and measures should adopt to cease this residue.

A review of analytical procedures for the simultaneous determination of medically important veterinary antibiotics in environmental water: Sample preparation, liquid chromatography, and mass spectrometry

Medically important (MI) antibiotics are defined by the United States Food and Drug Administration as drugs containing certain active antimicrobial ingredients that are used for the treatment of human diseases or enteric pathogens causing food-borne diseases. The presence of MI antibiotic residues in environmental water is a major concern for both aquatic ecosystems and public health, particularly because of their potential to contribute to the development of antimicrobial-resistant microorganisms. In this article, we present a review of global trends in the sales of veterinary MI antibiotics and the analytical methodologies used for the simultaneous determination of antibiotic residues in environmental water. According to recently published government reports, sales volumes have increased steadily, despite many countries having adopted strategies for reducing the consumption of antibiotics. Global attention needs to be directed urgently at establishing new management strategies for reducing the use of MI antimicrobial products in the livestock industry. The development of standardized analytical methods for the detection of multiple residues is required to monitor and understand the fate of antibiotics in the environment. Simultaneous analyses of antibiotics have mostly been conducted using high-performance liquid chromatography-tandem mass spectrometry with a solid-phase extraction (SPE) pretreatment step. Currently, on-line SPE protocols are used for the rapid and sensitive detection of antibiotics in water samples. On-line detection protocols must be established for the monitoring and screening of unknown metabolites and transformation products of antibiotics in environmental water.

Analysis of Major Components of Bacitracin, Colistin and Virginiamycin in Feed Using Matrix Solid-phase Dispersion Extraction by Liquid Chromatography-electrospray Ionization Tandem Mass Spectrometry

A quantitative LC-MS/MS method has been developed for simultaneous determination of bacitracin A, bacitracin B, colistin A, colistin B and virginiamycin M1 in feed. This rapid simple and effective extraction method was based on matrix solid-phase dispersion. Qualitative and quantitative analyses were performed by LC-ESI-MS/MS. CCβ of polypeptide antibiotics upon the method ranged from 9.6 to 15.8 μg kg-1 and 19.4 to 27.5 μg kg-1, respectively. The limit of quantification of polypeptide antibiotics was 25 μg kg-1 in feed samples. The recoveries of polypeptide antibiotics spiked in feed samples at a concentration range of 25-100 μg kg-1 were found above 75.9-87.9% with relative standard deviations within days less than 15.7% and between days less than 20.6%. This rapid and reliable method can be used to efficiently separate, characterize and quantify the residues of polypeptide antibiotics in feed with advantages of simple pretreatment and environmental friendly.

Development, validation and application of an ultra high performance liquid chromatographic-tandem mass spectrometric method for the simultaneous detection and quantification of five different classes of veterinary antibiotics in swine manure

In this study, a fast, simple and selective ultra high performance liquid chromatographic-tandem mass spectrometric (UHPLC-MS/MS) method for the simultaneous detection and quantification of colistin, sulfadiazine, trimethoprim, doxycycline, oxytetracycline and ceftiofur and for the detection of tylosin A in swine manure was developed and validated. First, a simple extraction procedure with acetonitrile and 6% trichloroacetic acid was carried out. Second, the supernatant was evaporated and the pellet was reconstituted in 1 ml of water/acetonitrile (80/20) and 0.1% formic acid. Extracts were filtered and analyzed by UHPLC-MS/MS on a Kinetex C18 column using gradient elution. The method developed was validated according to the criteria of Commission Decision 2002/657/EC. Recovery percentages varied between 94% and 106%, repeatability percentages were within the range of 1.7-9.2% and the intralaboratory reproducibility varied between 2.8% and 9.3% for all compounds, except for tylosin A for which more variation was observed resulting in a higher measurement uncertainty. The limit of detection and limit of quantification varied between 1.1 and 20.2 and between 3.5 and 67.3 μg/kg, respectively. This method was used to determine the presence and concentration of the seven antibiotic residues in swine manure sampled from ten different manure pits on farms where the selected antibiotics were used. A link was found between the antibiotics used and detected, except for ceftiofur which is injected at low doses and degraded readily in swine manure and was therefore not recovered in any of the samples. To the best of our knowledge, this is the first method available for the simultaneous extraction and quantification of colistin with other antibiotic classes. Additionally, colistin was never extracted from swine manure before. Another innovative aspect of this method is the simultaneous detection and quantification of five different classes of antibiotic residues in swine manure.

Analysis and behavior of colistin during anaerobic fermentation

A new analytical method for the determination of colistin in fermenter samples was developed followed by a study on the behavior of this substance during anaerobic fermentation. Analysis of colistin A and B was carried out by liquid chromatography-tandem mass spectrometry. Separation of the analytes was performed on a Security Guard column (4×3mm). Fourteen fermentation tests in batch as well as in continuous reactors were carried out. After 44days of anaerobic digestion of cattle manure, initially spiked with 500mg/kg of colistin sulfate, a considerable decrease of the colistin concentration to less than 1mg/kg could be observed. Furthermore, the daily production of biogas and methane was measured. A correlation between gas production and colistin concentration could not be determined. However, an increase of 10% of the cumulative methane production was observed in those fermenters spiked with an initial bolus of 500mg/kg colistin.

Simultaneous immunochemical detection of four banned antibiotic growth promoters in raw and cooked poultry tissue

Spiramycin, tylosin, bacitracin and virginiamycin are among a group of antibiotic growth promoters that have been banned in the European Union since the 1999 Council. This was due to concerns over the development of resistant bacteria emerging between humans and animals with the threat of antibiotics no longer being able to be used effectively to treat human infections. A sensitive and fast immunochemical method is presented for the determination of these four antibiotic growth promoters simultaneously in poultry tissue. The method employs methanol extraction followed by sample clean-up by solid-phase extraction (SPE) with determination by enzyme-linked immunoabsorbant assay (ELISA). The limit of detection (LOD) was less than 1 ng g(-1) and the detection capability (CCβ) was 3 ng g(-1) or less for all four antibiotic growth promoters. Validation was completed with both raw and cooked chicken, therefore either matrix could be used for the monitoring of these banned drugs. In a feeding trial no residues of either bacitracin or virginiamycin were found in medicated birds even without a withdrawal period. In the case of tylosin and spiramycin much higher residues level were detected immunochemically than was the case by mass spectrometry.

Validation of a novel LC-MS/MS method for the quantitation of colistin A and B in human plasma

A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method, characterized by complete automation and high-throughput, was developed for the determination of colistin A and B in human plasma. All sample preparation procedures were performed by using 2.2 mL 96-deep-well plates, whereas robotic liquid-handling workstations were utilized for all liquid transfer steps, including solid-phase extraction (SPE). The whole preparation procedure was very rapid, whereas the method had a very short chromatographic run time of just 2 min. Sample analysis was performed by reversed phase LC-MS/MS, with positive electrospray ionization, using multiple reaction monitoring. The absence of available purified colistin A and B standards led to the development of a novel LC method with evaporative light-scattering detector for the determination of their stoichiometries in the standard mixture, along with its purity. The proposed bioanalytical method was fully validated and it was proven to be selective, accurate, precise, reproducible and suitable for the determination of colistin A and B in human plasma. It was applied successfully to a pharmacokinetic study for the determination of both analytes in samples of patients.

Brain penetration of colistin in mice assessed by a novel high-performance liquid chromatographic technique

A sensitive and reliable liquid chromatographic method was developed and validated for the determination of colistin concentrations in mouse brain homogenate. With a mobile phase consisting of acetonitrile-tetrahydrofuran-water (50:25:25 [vol/vol]) at a flow rate of 1 ml/min, a linear correlation between peak area and colistin concentration was observed over the concentration range of 93.8 to 3,000 ng/g in brain tissue (R2 > 0.994). Intra- and interday coefficients of variation were 5.1 to 8.3% and 5.8 to 8.5%, respectively, and the recovery ranged from 85% to 94%. This assay was then utilized to determine the amount of colistin that permeated the blood-brain barrier over a 2-h period following bolus intravenous administration of colistin sulfate to mice. After a single dose of 5 mg/kg of body weight to mice, brain homogenate concentrations of colistin were very low, relative to plasma colistin concentrations, suggesting that colistin permeability across the healthy blood-brain barrier is negligible during this experimental period.

Current literature in mass spectrometry

In order to keep subscribers up‐to‐date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (6 Weeks journals ‐ Search completed at 4th. Oct. 2006)